Sometimes a motor is equipped with an electromagnetic brake device for locking a motor rotation shaft at a specified position. As shown in FIG. 2; an electromagnetic brake device 100, which is commonly used, includes a rotating disc 101 fixed to a motor rotation shaft 200, a sliding disc 102 that is slidable in a direction so as to come close to and move away from the rotating disc 101, a spring member 103 that presses the sliding disc 102 against the rotating disc 101, and an electromagnet 104 that pulls the sliding disc 102 in a direction for moving away from the rotating disc 101 while being against spring force of the spring member 103.
Under a condition where the electromagnet 104 is not excited, the sliding disc 102 is pressed against the rotating disc 101 with the spring force. As a result, due to frictional force between the sliding disc 102 and the rotating disc 101, braking force acts on the motor rotation shaft 200 so that the motor rotation shaft 200 gets locked. Contrarily, when the electromagnet 104 is excited, the sliding disc 102 is pulled while being against the spring force, so that the braking force is canceled and the motor rotation shaft 200 becomes rotatable freely.
As a whole, the electromagnetic brake device 100 is shaped like a cylindrical form having a specified length; and while the motor rotation shaft 200 being placed through a center shaft hole 105 of the electromagnetic brake device 100, the electromagnetic brake device 100 is assembled into a rear end section of a motor. Furthermore, a rear end shaft part 201 of the motor rotation shaft 200, which goes through the center shaft hole 105 of the electromagnetic brake device 100 and protrudes from a rear end side, is generally supported through an intermediary of a bearing 202 by a motor end plate 203. In such a case, there appears a dead space 300 shaped like a ring, at an outer surrounding section of the bearing 202, between a rear end surface 100a of the electromagnetic brake device 100 and the motor end plate 203.